/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.engine.trigger.utils;

import org.apache.iotdb.db.conf.IoTDBDescriptor;
import org.apache.iotdb.db.engine.trigger.sink.api.Event;
import org.apache.iotdb.db.engine.trigger.sink.api.Handler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Each Trigger instantiate a ForwardQueue
 *
 * @param <T> Subclass of Event
 */
public class BatchHandlerQueue<T extends Event> {

    private static final Logger LOGGER = LoggerFactory.getLogger(BatchHandlerQueue.class);

    private final int queueNumber;
    private final int queueSize;
    private final int batchSize;
    private final AtomicInteger atomicCount = new AtomicInteger();

    private final ArrayBlockingQueue<T>[] queues;

    private final Handler handler;

    public BatchHandlerQueue(int queueNumber, int queueSize, int batchSize, Handler handler) {
        this.queueNumber =
                Math.min(
                        queueNumber,
                        IoTDBDescriptor.getInstance().getConfig().getTriggerForwardMaxQueueNumber());
        this.queueSize =
                Math.min(
                        queueSize,
                        IoTDBDescriptor.getInstance().getConfig().getTriggerForwardMaxSizePerQueue());
        this.batchSize =
                Math.min(batchSize, IoTDBDescriptor.getInstance().getConfig().getTriggerForwardBatchSize());
        this.handler = handler;
        queues = new ArrayBlockingQueue[this.queueNumber];
        for (int i = 0; i < queueNumber; i++) {
            queues[i] = new ArrayBlockingQueue<>(this.queueSize);
            Thread t =
                    new ForwardQueueConsumer(
                            handler.getClass().getSimpleName()
                                    + "-"
                                    + BatchHandlerQueue.class.getSimpleName()
                                    + "-"
                                    + i,
                            queues[i]);
            t.setDaemon(true);
            t.start();
        }
    }

    private int getQueueID(int hashCode) {
        return (hashCode & 0x7FFFFFFF) % queues.length;
    }

    public boolean offer(T event) {
        // Group by device or polling
        if (event.getFullPath() != null) {
            return queues[getQueueID(event.getFullPath().getDevice().hashCode())].offer(event);
        } else {
            return queues[getQueueID(atomicCount.incrementAndGet())].offer(event);
        }
    }

    public void put(T event) throws InterruptedException {
        // Group by device or polling
        if (event.getFullPath() != null) {
            queues[getQueueID(event.getFullPath().getDevice().hashCode())].put(event);
        } else {
            queues[getQueueID(atomicCount.incrementAndGet())].put(event);
        }
    }

    private void handle(ArrayList<T> events) throws Exception {
        handler.onEvent(events);
    }

    class ForwardQueueConsumer extends Thread {

        ArrayBlockingQueue<T> queue;

        public ForwardQueueConsumer(String name, ArrayBlockingQueue<T> queue) {
            super(name);
            this.queue = queue;
        }

        public void run() {
            final long maxWaitMillis = 500;
            final ArrayList<T> list = new ArrayList<>();
            long startMillis = System.currentTimeMillis();
            long restMillis = maxWaitMillis;
            while (true) {
                try {
                    T obj;
                    if (list.isEmpty()) {
                        obj = queue.take();
                    } else {
                        obj = queue.poll(restMillis, TimeUnit.MILLISECONDS);
                    }
                    if (obj != null) {
                        list.add(obj);
                        queue.drainTo(list, batchSize - list.size());
                        if (list.size() < batchSize) {
                            long waitMillis = System.currentTimeMillis() - startMillis;
                            if (waitMillis < maxWaitMillis) {
                                restMillis = maxWaitMillis - waitMillis;
                                continue;
                            }
                        }
                    }
                    handle(list);
                    list.clear();
                    startMillis = System.currentTimeMillis();
                } catch (InterruptedException e) {
                    break;
                } catch (Throwable t) {
                    LOGGER.error("ForwardTaskQueue consumer error", t);
                }
            }
        }
    }
}
